Jeremy Corbyn and Mark Sedwill.

Asif Hameed, The Independent

The temperature has been rising over Brexit. Dominic Cummings, the UK prime minister’s special adviser, has indicated that even if the government loses an autumn confidence vote and must ultimately call a general election, the PM may simply decide that polling day takes place after October 31. Since polling day is normally held on a Thursday, possible dates would include November 7 or 14. That would mean that Brexit would be delivered during a general election campaign, when parliament is not sitting. It could, of course, also mean that the UK would leave the EU without a deal while parliament isn’t sitting – even though MPs have repeatedly expressed their opposition to such a scenario.

As a matter of law, delaying polling day is permissible. The Fixed-term Parliaments Act 2011 simply states that polling day is set by the Queen on “the recommendation of the prime minister”. The exact timing is left open. The absence of any restriction is a striking statutory oversight. Perhaps the drafters never contemplated that a government on the losing side of a confidence vote would drag its heels over calling an election. Such political masochism would surely be penalised once polling day finally arrived. In fact, Brexit is reversing the incentive structure. Heel-dragging is suddenly advantageous for a government looking to avoid further wrangling with MPs.

But the question of whether a delay would comply with constitutional convention is a different matter. All constitutions comprise legal and non-legal rules. Constitutional conventions are non-legal rules that govern the behaviour of constitutional actors such as government ministers or the Queen.

The convention in question – variously called the caretaker convention or purdah – imposes restrictions on government activity if it has lost a confidence vote or in the run-up to polling day. As the cabinet manual explains: Among other things, the government should defer the appointment of senior public officials, and the “taking or announcing of major policy decisions” (paragraph 2.29).

Some have argued that the government would breach this convention – and thereby act unconstitutionally – if it allowed Brexit to take place on October 31 during an election campaign. They argue that it should instead request an Article 50 extension from the EU in these circumstances. Others disagree.

Labour leader Jeremy Corbyn is raising concerns about whether a delay would conform to constitutional convention. He has written to Mark Sedwill, cabinet secretary and head of the civil service, asking for his position on whether “the government should seek a time-limited extension to Article 50” if the country is in the midst of an election campaign.

But that is not the only question. Corbyn should also be asking whether the government would, in the first instance, breach the caretaker convention simply by recommending to the Queen that polling day take place after 31 October. In other words, would the very recommendation to the Queen be itself unconstitutional, given that the government knows that an important decision needs to be made about Brexit within the period it would be proposing for the election?

Parliament returns from summer recess on September 3, and if the opposition moves quickly to hold a confidence vote on that day, polling day could potentially be held on October 24. The major policy decision – whether or not to extend Article 50 – could then be taken by the new government, rather than being left adrift during an election campaign.

But in this case, there is time. A recommendation to the Queen to delay polling day would be a deliberate act to take that time away. Even if debate persists about what the caretaker convention requires in these circumstances, it would still be very easy to err on the side of caution. To be safe, the government could simply recommend an earlier polling day to the Queen.